Water heater dip tube construction



NOV. 15, 1966 BORDEAUX WATER HEATER DIP TUBE CONSTRUCTION Filed Dec.

United States Patent O 3,285,241 WATER HEATER DIP TUBE CONSTRUCTION Jean Bordeaux, Santa Ana, Calfi, assignor to Robertshaw Controls Company, 3 corporation of Delaware Filed Dec. 5, 1960, Ser. No. 73,648 4 Claims. (Cl. 126362) This invention relates to devices for eliminating stacking in water heaters.

In conventional water heater construction, a thermostat is located relatively close to the bottom of the tank with an immersion type sensing element extending into the water within the tank. Cold water enters the tank through a dip tube which hangs from the top of the tank and discharges water in the area adjacent the sensing clement of the thermostat. As hot water is drawn from the top of the tank, cold water is admitted to the lower portion which cools the sensing element and causes the burnor to corne on. This results in satisfactorv operation when relatively long draw-ofis are made. However, as a rule, the water temperature increases progressively from the lowermost portion of the tank to the uppermost portion. Accordingly, When a number of short draw-ofis are made, small amounts of cold water are admitted to the lower portion of the tank at frequent intervals to thereby cool the sensing element. As a result, the burner is on longer than is desirable and the temperature of the water at the top of the tank rises to undesirable and often dangerous levels. This condition is referred to in the trade as stacking.

This invention eliminates excessive temperatures caused by stacking in water heaters by mixing hot water from the top of the tank with incoming cold water.

Accordingly, it is an object of the present invention to prevent overheating of water in a hot water tank.

Another object of this invention is to prevent an excessive rise in temperature of the water at the top of a hot water tank.

Another specific object of this invention is to eliminate stacking in water heaters by mixing hot water from the top of the tank with incoming cold water.

In accordance with the invention, a venturi insert is mounted in the upper portion of the dip tube. As the incoming cold water passes through the venturi throat, there is a corresponding reduction in pressure. This reduction in pressure causes the surrounding hot water to enter the opening and mix with the cold water as it passes through the venturi. In a modification of this form, a temperature responsive device controls the venturi section.

Several specific forms of the invention will now be described for the purpose of illustrating the general principles 01: the invention.

In the drawings:

FIG. 1 is a schematic partial sectional view of a conventional water tank and heater with the device of the present invention installed therein;

FIG. 2 is an enlarged sectional view of a form of dip tube which may be applied to the tank of FIG. 1;

FIG. 3 is an enlarged sectional view of another form of the invention;

FIG. 4 is a view similar to FIG. 3 but illustrates a modification.

Referring to FIG. 1, a hot water heater is disclosed including a water heating and storage tank having its upper end provided with the usual cold water inlet 12 and the hot water outlet pipe 14. Mounted in the cold water inlet is an elongated pipe or dip tube 22 which extends to the lower portion of the tank and is open at the lower end. The water heater is further provided with the usual burner 20 connected with a gas inlet 16 and a 3,285,241 Patented Nov. 15, 1966 thermostatic control element 18. Positioned on the upper portion of the tube 22 is an element 56 which constitutes a device according to one form of the present invention.

Referring now to FIG. 2, dip tube 22 is provided at its upper portion with an aperture 32 in the wall thereof. The aperture 32 is normally closed by a bimetallic strip 28 which is attached to the dip tube wall by a rivet 30. The rivet 30 may be hollow to provide an anti-syphon hole as is customary in present dip tubes.

In operation, the bimetallic strip 28 acts to close the opening 32 until an undesirable overtemperature is reached in the water at the top of the tank. When this predetermned undesirable temperature is reached, the bimetallic strip 28 will then deflect away from opening 32 and permit cold water entering through the dip tube 22 to flow through opening 32 into the top of the tank, thereby 'reducing the temperature of the hot water in that area.

Normally, the difference in static head at the aperture 32 and the bottom of the dip tube 22 is sufiicient to cause substantial flow through the aperture 32 into the top of the tank. However, it is often desirable to increase flow by placing a restriction at the tube outlet, for example, by the use of an apertured cap 24 secured to the bottom of the dip tube 22.

At high flow rates (about 5 g.p.m.), there is a tendency for water to force the bimetal open by the velocity head acting through aperture 32. It is desirable to resist this force when the top tank temperature is not excessively high. The closing force exerted by the bimetal may be increased by a biasing opening 34 in the wall of the tube 22 between rivet 30 and aperture 32. This opening 34 is small in relation to the aperture 32 and when the bimetal is thermally distorted, water flows freely through aperture 32 with very little flow through opening 34. As the water temperature drops and the bimetal moves toward aperture 32, more cold water flows through opening 34. This causes a further drop in the bimetal temperature increasing the closing force.

Referring now to FIG. 3, where the claimed form of the invention is illustrated, a venturi insert 40 is fastened in the upper portion of the dip tube 22 by means of a hollow rivet 42. The hollow rivet 42 provides a passage 44 through the wall of the dip tube and the insert.

In operation, as cold water flows through the venturi of insert 40, there will be a corresponding reduction in pressure. This reduction in pressure will cause hot water to enter through passage 44 and mix with the cold water as it passes through the dip tube 22. Accordingly, water being discharged from the bottom of the dip tube 22 will be considerably warmer than the supply water and will condition the thermostat 16 to maintain the burner 18 on for shorter periods of time. Since the burner will be on for shorter periods of time, the stacking elIect will be reduced considerably.

The device shown in FIG. 4 is similar to that shown in FIG. 3 and illustrates a venturi insert 50 mounted in the upper portion of the dip tube 22 by means of a hollow rivet 52 having passage 54 therethrough. A bimetallic strip 56 is mounted on the outer wall of the dip tube 22 as by spacer 58 and screw 60. Bimetal 56 is so positioned that it closes passage 54 when the water at the top of the tank does not exceed a predetermined temperature. The bimetal strip 56 thus performs a similar function to bimetal 28 of FIG. 2 in that it permits the mixing operation to take place only When excessive temperatures are experienced et the top of the tank. The bimetal 56 may be further provided with a restricted aperture 62 overlying passage 54 for providing an antisyphoning means.

It will be understood that many changes may be made in the details of construction and arrangement et parts to accomplish the purposes of this invention without depart ing from the scope -of the invention as defined in the appended daims.

I daim:

1. In a water heater having a thermostatically contr0lled burner, the combination including a tank, a cold water inlet in the top of said tank, a hot water outlet in the top of said tank, a dip tube attached to said tank at said tank, means including a venturi insert in said tube for mixing the water at the top of said tank with the incoming co1d water to prevent exoessivdy high temperatures at the top of said tank, and fastener means mounting said venturi insert in said tube and having an opening therein connecting the interior of said tube with the .surrounding water in said tank whereby incoming cold water passing through said venturi insert will cause the water surrounding said tube at said opening to enter said opening and mix With said incoming c0ld water.

2. Apparatus as defined in daim 1 further including a bimetallic element on the outer wall of said tube normally dosing said opening.

3. The structure defined in daim 1 wherein said means mounting said venturi insert tube is a hollow rivet.

4. The structure defined in daim 3 wherein said rivet has portions projecting laterally on its opposite ends into cold water inlet extending to the lower portion of said 4' respective engagement with the venturi insert and the external surface of said dip tube.

References Cited by the Examiner UNITED STATES PATENTS 1,334,446 3/1920 Good 15828 1,681,377 8/1928 Stack 126362 XR 2,012,101 8/1935 Hynes.

2,025,256 12/ 1935 Thomas 12214 2,062,507 12/ 1936 Ray-Engleheart --a-- 239-434 2,065,148 12/1936 Nallinger 23634.5 2,115,601 4/1938 Whitby et a]. 126351 XR 2,176,331 10/1939 Drapeau 23634.5 2,294,163 8/ 1942 Donndly et al. 12214 2,504,092 4/1950 Thomas 122-17 2,592,863 4/1952 Conner 126362 X-R 3,019,986 2/1962 Schoerner 236-12 3,027,088 3/1962 Goehring 23612 FOREIGN PATENTS 282,075 8/ 1928 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

PERCY L. PATRICK, Examiner.

ROBERT A. DUA, Assistant Examiner. 

1. IN A WATER HEATER HAVING A THERMOSTATICALLY CONTROLLED BURNER, THE COMBINATION INCLUDING A TANK, A COLD WATER INLET IN THE TOP OF SAID TANK, A HOT WATER OUTLET IN THE TOP OF SAID TANK, A DIP TUBE ATTACHED TO SAID TANK AT SAID COLD WATER INLET EXTENDING TO THE LOWER PORTION OF SAID TANK, MEANS INCLUDING A VENTURI INSERT IN SAID TUBE FOR MIXING THE WATER AT THE TOP OF SAID TANK WITH THE INCOMING COLD WATER TO PREVENT EXCESSIVELY HIGH TEMPERATURES AT THE TOP OF SAID TANK, AND FASTENER MEANS MOUNTING SAID VENTURI INSERT IN SAID TUBE AND HAVING AN OPENING THEREIN CONNECTING THE INTERIOR OF SAID TUBE WITH THE SURROUNDING WATER 